/Engine/Source/Runtime/InteractiveToolsFramework/Public/BaseTools/ClickDragTool.h
UClickDragToolis a base tool that basically just implementsIClickDragBehaviorTarget, and on setup registers aUClickDragInputBehavior. You can subclass this Tool to implement basic click-drag type Tools. If you want to do more advanced things, like handle modifier buttons/keys, you will need to implementIClickDragBehaviorTargetyourself
class UClickDragTool : public [UInteractiveTool](API\Runtime\InteractiveToolsFramework\UInteractiveTool), public [IClickDragBehaviorTarget](API\Runtime\InteractiveToolsFramework\BaseBehaviors\IClickDragBehaviorTarget)